The present inventors are not the first to disclose a suspended magnetic stirrer wherein the stirrer, i.e., shaft and impeller, is totally enclosed within a vessel. An early disclosure is U.S. Pat. No. 2,932,493 to Jacobs. In FIG. 3, Jacobs describes a beverage mixer having a magnetic stirrer suspended from a lid by means of a ball and socket joint.
A second disclosure of interest is U.S. Pat. No. 3,854,704 to Balas. A gimbaled bearing (ball and socket joint) attached to a closure is illustrated in FIGS. 8 and 9. As used in cell culture, this stirrer also is envisioned to operate in an arcuate manner.
Finally, a recently issued patent, U.S. Pat. No. 4,289,854 to Tolbert et al., relates an allegedly novel stirrer using a flexible sail impeller. Used in the suspension culturing of mammalian cells, the impeller centrally rotates about a bearing suspended from a stopper. The bearing consists of two parts: a downwardly projecting, rigid stationary shaft which flares outwardly to provide a lower bearing surface; and a rotatable sleeve member internally journalled to form an upper, rotating bearing surface.
While all of these disclosures are relevant to any discussion of enclosed magnetic stirrers, they do not disclose or suggest the novel and non-obvious features of the present invention.